1. Technical Field
The present invention relates to a recording head unit appropriate for an ink-jet recording apparatus for ejecting ink droplets to record images, such as characters, on a recording medium.
2. Related Art
Some of ink-jet recording apparatuses (hereinafter referred to as xe2x80x9crecording apparatusesxe2x80x9d), such as printers, plotters and facsimile machines, have a recording head unit obtained by integrally forming a cartridge holder to which an ink cartridge is replaceably mounted, and a recording head for ejecting ink as a pressure generating element is activated. In use, an ink cartridge is mounted to the cartridge holder of the recording head unit, so that the ink contained in the ink cartridge is supplied to the recording head via an ink flow path. The recording head can be continuously used for an extended period of time by replacing the ink cartridge.
The recording head unit of this type is required to prevent a foreign substance, such as dust, from entering the recording head, because the entering substance causes ink clogging or a feeding failure. Therefore, the recording head unit generally has a filter located inside an ink supply needle that is inserted into the ink cartridge. After undesirable substances have been removed from the ink by the filter, the ink is supplied to the recording head.
To surely prevent the foreign substrate from entering the recording head unit of this type, the unit is subjected to the following cleaning process during the manufacture. That is, foreign substances present along the ink flow path downstream of the filter are removed by first supplying a cleaning liquid in the direction in which the ink flows and then in the opposite direction. Since if this process is improperly performed not all foreign substances will be removed, and they will later, during ordinary use, be carried into the recording head, this cleaning process is performed for an adequate long period of time for completeness.
Demands exist for smaller recording heads and larger capacity ink cartridges. This is because smaller recording heads will make it possible to reduce manufacturing costs, and larger capacity ink cartridges will enhance user convenience. Manufacturing costs will come down if the size of a recording head is reduced because component part sizes will also be reduced, as in the case for a silicon flow path formation substrate, one of the more expensive parts used in a recording head, for which the cost of production will drop because a single silicon wafer will yield more substrates. And enhanced user convenience will be provided if the capacity of ink cartridges is increased because more print will be executed with a single cartridge and the ink cartridge replacement cycle will be extended.
However, to increase the sizes of ink cartridges and to reduce the sizes of recording heads, extended ink flow paths will be needed, and accordingly, longer cleaning times will be required. And if cleaning times are increased, manufacturing costs will rise because manufacturing efficiency will be reduced. This is unavoidable because if to avoid a rise in production costs the cleaning times were maintained or were shortened, ink flow paths would be insufficiently cleaned and not all foreign substances would be removed, and the yield would be reduced.
To resolve these problems, it is one objective of the present invention to provide a recording head unit that can surely prevent the entry of any foreign substances into a recording head.
It is another objective of the invention to provide a recording head unit that can be efficiently manufactured even when an ink flow path is extended.
To achieve the above objectives, according to a first aspect of the invention, a recording head unit comprises:
a cartridge holder adapted to replaceably mount at least one an ink cartridge defining a plurality of ink chambers;
a recording head, for ejecting ink in response to activation of a pressure generating element;
a plurality of ink flow paths through which ink in the ink chambers is supplied to the recording head, respectively, each of the ink flow paths including a first communication path communicated with an ink outlet of the corresponding ink chamber, a second communication path communicated with a corresponding ink inlet of the recording head, and a convergent flow path communicating the first communication path with the second communication path, the convergent flow paths being arranged to converge toward the recording head; and
filters respectively disposed in the second communication paths.
The phrase xe2x80x9cat least one ink cartridge defining a plurality of ink chambersxe2x80x9d is intended to mean not only a single ink cartridge having a plurality of ink chambers, but also a plurality of ink cartridges, each having a single ink chamber. Of course, a combination of these ink cartridges also falls within the scope of this phrase so long as a plurality of ink chambers are defined.
According to a second aspect, in the recording head unit of the first aspect, each of the convergent flow paths is downwardly inclined from the corresponding first communication path to the second corresponding communication path.
According to a third aspect, in the recording head unit of the first aspect, each of the convergent flow paths extends horizontally.
It should be noted that the horizontal direction includes an inclination that does not greatly affect head difference.
According to a fourth aspect, in the recording head unit of the third aspect, the convergent flow paths are formed in a convergent flow path unit in the form of a plate.
According to a fifth aspect, in the recording head unit of the fourth aspect, the convergent flow path unit includes a flow path grooved plate having a plurality of flow path grooves for forming the convergent flow paths, and a lid plate for closing openings of the flow path grooves.
According to a sixth aspect, in the recording head unit of the fifth aspect, the lid plate has flexible portions at least partially sealing the flow path grooves, and each of the flexible portions is elastically deformable by pressure change in the ink flowing along the corresponding convergent flow path.
According to a seventh aspect, in the recording head unit of the fifth or sixth aspect, a first communication portion provided with the first communication paths is integral with the lid plate.
According to an eighth aspect, in the recording head unit of one of the fifth to the seventh aspects, the second communication paths are formed in the flow path groove plate, and filter holders, for holding the filters, are positioned at the upstream ends of the second communication paths.
According to a ninth aspect, in the recording head unit of one of the fifth to the eighth aspects, protrusions are formed, on joining face of the lid plate to the flow path grooved plate, that are narrower than widths of the openings of the flow path grooves and lower than depths of the flow path grooves; and wherein, when the lid plate and the flow path grooved plate are joined together in a state that the protrusions are fitted to the flow path grooves, gaps are defined between side walls of the protrusions and inner walls of the flow path grooves.
According to a tenth aspect, in the recording head unit of the fourth aspect, the convergent flow path unit comprises an opening plate, in which through holes that serve as the convergent flow paths are formed in the direction of the thickness of the convergent flow path unit, an upper lid plate, for sealing upper openings of the through holes, and a lower lid plate, for sealing lower openings of the through holes.
According to an eleventh aspect, in the recording head unit of the tenth aspect, a first communication unit, a first communication portion provided with the first communication paths, is an integral with the upper lid plate.
According to a twelfth aspect, in the recording head unit of the tenth and the eleventh aspects, the second communication paths are formed in the lower lid plate, and filter holders, for holding the filters, are located at upstream ends of the second communication paths.
According to a thirteenth aspect, in the recording head unit of the fourth aspect, the convergent flow path unit includes an upper flow path grooved plate, in which upper flow path grooves are formed to constitute upper portions of the convergent flow paths, and a lower flow path grooved plate, in which lower flow path grooves are formed to constitute lower portions of the convergent flow paths.
According to a fourteenth aspect of the invention, in the recording head unit of the thirteenth aspect, the second communication paths are formed in the lower flow path grooved plate, and filter holders, for holding the filters, are positioned at upstream ends of the second communication paths.
According to a fifteenth aspect of the invention, in the recording head unit of the seventh or eleventh aspect, the first communication portion is constituted by ink supply needles that are inserted into the at least one ink cartridge to supply ink from the ink chambers.
According to a sixteenth aspect of the invention, in the recording head unit of one of the fourth to the fifteenth aspects, at least one of plates that constitute the convergent flow path unit is formed of a transparent or semi-transparent material.
Here, the term transparent or semi-transparent material is intended to mean a material through which objects on its opposite side are visible.
According to a seventeenth aspect of the invention, in the recording head unit of one of the fourth to sixteenth aspects, plates constituting the convergent flow path unit are joined together by thermal welding.
According to an eighteenth aspect of the invention, in the recording head unit of one of the fourth to sixteenth aspects, plates constituting the convergent flow path unit are joined together by an adhesive.
According to a nineteenth aspect of the invention, in the recording head unit of the eighteenth aspect, the adhesive flows easily, and recessed portions in which excessive adhesive can be accommodated are formed around adhered areas.
According to a twentieth aspect of the invention, in the recording head unit of one of the fourth to sixteenth aspects, plates that constitute the convergent flow path unit are joined together by ultrasonic welding.
According to a twenty-first aspect of the invention, in the recording head unit of one of the first, seventh, ninth to eleventh, thirteenth, and fifteenth to twentieth aspects, the filters are located at intermediate portions of the second communication paths; and wherein portions of the second communication paths, upstream of the filters, are increased in diameter as the portions approach the filters.
According to a twenty-second aspect of the invention, in the recording head unit of one of the first to twenty-first aspects, portions of the second communication units, downstream of the filters, are decreased in diameter toward a downstream side to present a funnel shape.
According to a twenty-third aspect of the invention, in the recording head unit of one of the first to twenty-second aspects, air bubble holding spaces, in which air bubbles are to be retained, are formed in intermediate portions of the ink flow paths.
According to a twenty-fourth aspect of the invention, in the recording head unit of the twenty-third aspect, the air bubble holding spaces include first air bubble holding spaces formed by partially increasing the diameters of the first communication paths.
According to a twenty-fifth aspect of the invention, in the recording head unit of the twenty-third or twenty-fourth aspect, the air bubble holding spaces include second air bubble holding spaces formed by partially increasing the diameters of the ink flow paths, the second air bubble holding spaces being adjacent to an upstream of the filters.
According to a twenty-sixth aspect of the invention, in the recording head unit of the twenty-third aspect, the air bubble holding spaces include first air bubble holding spaces, formed by partially increasing the diameters of the first communication paths, and second air bubble holding spaces, formed by partially increasing the diameters of ink flow paths, the second air bubble holding spaces being adjacent to and upstream of the filters; and wherein the volume of each of the first air bubble holding spaces is greater than the volume of each of the second air bubble holding spaces.
According to a twenty-seventh aspect of the invention, in the recording head unit of one of the second to twenty-sixth aspects, ceiling faces of the convergent flow paths incline upward from the second communication paths to the first communication paths.
According to a twenty-eighth aspect of the invention, in the recording head unit of one of the first to twenty-seventh aspects, different types of ink are stored in the ink chambers; and wherein the ink flow paths are respectively formed for the different types of ink.
The phrase xe2x80x9ctypes of inkxe2x80x9d is intended to mean not only ink types different in color, but also ink types different in coloring material, such as dye-based ink and pigment-based ink, and ink types of high permeability and low permeability, i.e., different in permeability relative to recording media.
According to a twenty-ninth aspect of the invention, in the recording head unit of one of the first to twenty-eighth aspects, the convergent flow paths have the same length.
According to a thirtieth aspect of the invention, the recording head unit of one of the first to twenty-ninth aspects further includes:
nozzle openings, through which ink droplets are to be ejected; and
pressure generation chambers communicated with the nozzle openings,
wherein ink pressure in a desired one of the pressure generation chambers is changed by the pressure to eject the ink droplets through the corresponding nozzle opening, and
wherein piezoelectric vibrators, which can vary the volumes of the respective pressure generation chambers, are employed as the pressure generating element.
According to a thirty-first aspect of the invention, in the recording head unit of the thirtieth aspect, the piezoelectric vibrators are piezoelectric vibrators of a vertical vibration mode.
According to a thirty-second aspect of the invention, the recording head unit of one of the first to twenty-ninth aspects further comprises:
nozzle openings, through which ink droplets are ejected; and
pressure generation chambers communicated with the nozzle openings,
wherein ink pressure in a desired one of the pressure generation chambers is changed by the pressure generating element to eject the ink droplets through the corresponding nozzle opening, and
wherein heat generation devices that can generate air bubbles in the respective pressure generation chambers are employed as the pressure generating element.
The present disclosure relates to the subject matter contained in Japanese patent application No. 2000-051362 (filed on Feb. 28, 2000), Japanese patent application No. 2000-083589 (filed on Mar. 24, 2000), Japanese patent application No. 2000-108351 (filed on Apr. 10, 2000), Japanese patent application No. 2000-302039 (filed on Oct. 2, 2000), and Japanese patent application No. 2001-027672 (filed on Feb. 5, 2001), which are expressly incorporated herein by reference in their entireties.